JPH059399A - Method for producing disazo pigment - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing a disazo pigment excellent in hiding power. [Composition] In a method for producing a disazo pigment, in which a disazo pigment slurry obtained by coupling a tetrazo solution of benzidines and a coupler solution containing acetoacetanilide is heat-treated, an alkali region is adjusted after coupling or after coupling. A method for producing a disazo pigment, characterized in that the water-soluble impurities contained in the slurry are removed from the pigment slurry and reslurried, and then the above heat treatment is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a disazo pigment, and more particularly to a process for producing a disazo pigment which can be adjusted to have a hiding power.

[0002]

2. Description of the Related Art Since primary particles of a pigment after coupling in the synthesis of a disazo pigment are extremely fine, if they are filtered out in this state and dried, strong agglomeration occurs, and the primary particles should be dispersed at the time of ink preparation. Is impossible. Along with this, hiding power becomes unsatisfactory. Therefore, generally, a method is employed in which the slurry after coupling is heat-treated to grow primary pigment particles. However, there was a limit to the hiding power and the like only by raising the heating temperature or lengthening the heating time.

[0003]

The present invention relates to a method for producing a disazo pigment, and more particularly to a method for producing a disazo pigment capable of obtaining an ink having excellent hiding power when used in an aqueous flexo ink.

[0004]

The present invention provides a method for producing a disazo pigment in which a disazo pigment slurry obtained by coupling a tetrazo solution of benzidines and a coupler solution containing acetoacetanilide is heat-treated. Alternatively, the present invention relates to a method for producing a disazo pigment, characterized in that after the coupling, the water-soluble impurities contained in the slurry are removed from the pigment slurry adjusted to the alkaline region and then reslurried, followed by the heat treatment.

According to the present invention, a tetrazo component such as 3,3'-dichlorobenzidine or 2,2 ', 5,5'-tetrachlorobenzidine and a coupling component selected from acetoacetanilides are first coupled. To obtain a pigment slurry. Specific examples of acetoacetanilides include, for example, acetoacetanilide, acetoaceto-
o-toluidide, acetoacet-m-xylidide, acetoaceto-o-anisidide, acetoaceto-2,5-dimethoxyanilide, acetoaceto-p-anisidide, acetoaceto-2,5-dimethoxy-4-chloroanilide, acetoaceto-o-chloroanilide. Etc. The coupling method may be a known method.

After filtering the pigment slurry obtained by coupling, it is washed with 10 to 200 times the amount of water of the pigment,
The pigment cake is reslurried in water and then heated. The heating temperature is not particularly limited, but is 40 to 130 ° C, preferably 70 to 100 ° C. The heating time may be 30 minutes or more. Then, the pigment slurry is filtered and washed with water to obtain the disazo pigment of the present invention.

In the above step of filtering the pigment slurry obtained by coupling and washing with water, the same treatment may be carried out after the pH of the pigment slurry is adjusted to the alkaline side.
The alkaline pH at this time is in the range of pH 8 to pH 13.

The present invention will be described below with reference to examples. In the examples, parts and% represent parts by weight and% by weight.

(Example 1) 25.3 parts of 3,3'-dichlorobenzidine were tetrazotized by a conventional method to obtain a tetrazo solution. On the other hand, 35.4 parts of acetoacetanilide was prepared according to a conventional method, and the tetrazo solution was coupled to this prepared solution. The resulting pigment slurry was filtered, washed with 3 liters of water, and the pigment cake was reslurried in water. Then, it was heated to 95 ° C., left for 60 minutes, filtered, washed with water and dried.

Example 2 In Example 1, the pigment cake was reslurried in water and then placed in an autoclave for 120 hours.
Heated to ° C. After standing for 30 minutes, this slurry was filtered, washed with water and dried.

(Comparative Example 1) In Example 1, the pigment slurry after coupling was heated to 95 ° C. After standing for 60 minutes, this slurry was filtered, washed with water and dried.

Flexographic inks were prepared by blending the pigments obtained in Examples 1 and 2 and Comparative Example 1 into a water-soluble acrylic flexographic ink varnish so that the pigment content was 16%. It was developed on a test paper with a black band using a proofer and evaluated for hue, gloss and hiding power.
With respect to gloss, 60-degree gloss was measured using a gonio gloss meter, and as to hiding power, the difference in E value between a white background and a black background was measured using a colorimeter.

The results are shown in Table 1, and the hiding power of the present invention was particularly excellent. Table 1 Results of evaluation with water-soluble acrylic flexo ink

[0014]

[Table 1]

[0015]

EFFECT OF THE INVENTION The heat treatment of the pigment slurry has the effect of growing the pigment crystals to control the particle size and, at the same time, preventing dry aggregation. By removing the impurities present at the end of the coupling, crystal growth of the pigment became smooth, and as a result, gloss, hiding power, etc. were improved.

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[Procedure amendment]

[Submission date] August 30, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction content]

According to the present invention, first, a tetrazo component such as 3,3'-dichlorobenzidine or 2,2 ', 5,5'-tetrachlorobenzidine and a coupling component selected from acetoacetanilides are coupled. To obtain a pigment slurry. Specific examples of acetoacetanilides include, for example, acetoacetanilide, acetoaceto-
o-toluidide, acetoacet-m-xylidide, acetoaceto-o-anisidide, acetoaceto-2,5-dimethoxyanilide, acetoaceto-c-anisidide, acetoaceto-2,5-dimethoxy-4-chloroanilide, acetoaceto-o-chloroanilide and the like. There is. The coupling method may be a known method.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Flexographic inks were prepared by blending the pigments obtained in Examples 1 and 2 and Comparative Example 1 into a water-soluble acrylic flexographic ink varnish so that the pigment content was 16%. It was developed on a test paper with a black band using a proofer and evaluated for hue, gloss and hiding power.
For gloss, 60-degree gloss was measured using a gonio-gloss meter, and for hiding power, the difference (Δ (Δ
E)) was measured using a colorimeter.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

[Table 1]

Claims (1)

Claim: What is claimed is: 1. A method for producing a disazo pigment, which comprises heat-treating a disazo pigment slurry obtained by coupling a tetrazo solution of benzidines and a coupler solution containing acetoacetanilides, and A method for producing a disazo pigment, characterized in that after the coupling is completed, the water-soluble impurities contained in the slurry are removed from the pigment slurry adjusted to the alkaline region and then reslurried, and the above heat treatment is carried out.